Abstract
In the last years, an increasing number of countries has been affected by water shortage. Seawater desalination driven by solar energy, which is usually available in arid regions, might be a solution to satisfy the freshwater demand. In this study, the feasibility of a stand-alone multi-effect desalination (MED) plant driven by solar energy for an isolated community was studied. The system was made up of a solar field, a MED unit, and a thermal storage that mitigated solar energy fluctuations. Simulations with different top brine temperature and inclination and number of the solar panels were carried out in Matlab and Aspen Plus on an hourly basis by considering one typical meteorological year for ambient temperature and solar radiation. Two different sources of electrical energy were considered: A photovoltaic (PV) field and a diesel generator. The results were compared from an energetic and economic point of view, by considering the adoption of plastic as a material for MED heat exchangers. The maximum water production was obtained with December as the design month. Polytetrafluoroethylene heat exchangers allowed the cost of water to be reduced up to 9.5% compared to conventional exchangers. The lowest cost of water (7.09 $/m3) was obtained with September as the design month and a tilt angle of 45° with the PV field as the electrical power source.
Highlights
Water is an essential element for human life
The number of collectors (Ncoll ) was determined as a function of the top brine temperatures (TBT), the design month, and the tilt angle to produce the thermal energy required by the multi-effect desalination (MED) in the average day of the h i month (Q)
The2020, number of collectors of the solar field is shown in Figure 2 for each TBT, design month, and tilt17
Summary
Water is an essential element for human life. The growth of the world population and ever higher standard of life are causing an exponential increase of freshwater demand. Compared three different systems for small-scale MED desalination: a conventional system using a steam and diesel generator; a solar-assisted system in which solar collectors provided the thermal energy and a diesel generator provided the pumping power; a solar system in which the thermal energy was supplied by solar collectors and pumping power by solar photovoltaic (PV) His results confirm that even if solar energy cannot currently compete with fossil energy, the use of solar energy can be an attractive alternative in many remote, arid and sunny areas of the world due to the higher cost of fuel transportation [8]. Two cases were considered to produce the electrical power required by the plant: A PV field and a diesel generator These two cases were compared in terms of production cost of water (COW). The adoption of plastic heat exchangers is an important factor to reduce water cost in small-scale thermodynamic desalination systems
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